Method of stopping and restarting an internal combustion engine with indirect injection

ABSTRACT

The speed of rotation and the angular position of the rotating part ( 2, 3 ) of the engine ( 1 ) are measured continuously, and the fuel injection is cut off at predetermined speed and angular position values of the rotating part ( 2, 3 ) in order to stop the engine in a predetermined position that facilitates restarting the engine. In order to restart the engine, using a starter ( 4 ), fuel is injected into at least one cylinder of the engine when the piston moving in the cylinder is in a determined position. The spark ignition and/or fuel injection is interrupted at predetermined speed and angular position values of the rotating part ( 2, 3 ) of the engine ( 1 ), and fuel is injected into at least one cylinder of the engine ( 1 ) during the last revolution of the engine before stopping. In order to restart the engine, ignition is carried out in at least one cylinder, the piston of which is in the compression position at the moment when the engine ( 1 ) stops.

The invention relates to a method of stopping and restarting an internalcombustion engine with indirect injection.

Internal combustion engines comprise at least one piston that can bemoved in a reciprocating manner in a cylinder, and generally a pluralityof mounted pistons that are each movably mounted in a cylinder, thepiston or each of the pistons being connected to a crankshaft by aconnecting rod driving the crankshaft in rotation about a shaft.

The conditions for restarting a thermal engine, after the moving partsof the engine have stopped, i.e., in particular, the pistons and thecrankshaft, are highly dependent on the stopping position of the movingparts. The power required to restart an engine can vary, for example,between a minimum value and a maximum value, which is 30% greater thanthe minimum value. Moreover, the time required to restart an engine(calculated, for example, in terms of the number of revolutions of thecrankshaft) is also highly dependent on the stopping conditions of theengine, in the case of both spark ignition engines and compressionignition engines.

In the case of an in-line four-cylinder engine, there are four possibleengine stopping positions, in which the positions of the pistons aredifferent, between the top dead centers and the bottom dead centers ofthese pistons. The stopping position of a four-cylinder engine is thusdefined to within 180°, i.e. with an approximation of half a revolutionwith regard to thug position of the crankshaft.

Moreover, around these stopping positions, the friction of the movingparts of the engine causes a dispersion of the order of a plurality oftens of degrees (for example, 30°).

These dispersions of the stopping points of the engine result inirregularities during starting, considerable starting times andpollution, which can be significant and which is poorly controlled,owing to incomplete combustion in the cylinders.

It has been proposed that the position of the moving parts of the engineshould be controlled, during the stoppage of the engine, or rectified,after the engine has stopped, using an auxiliary electric machine. It istherefore necessary to use a specific electric machine and means ofcontrolling this electric machine for braking or returning the engine toits stopping position. In the case of engines of modern design, withindirect injection, i.e. with injection of fuel into the inlet manifoldsof the engine, there is a particularly precise and sensitive means thatis associated with control means, such as a computer, for synchronizingthe fuel injection with the positions of the pistons in the cylinders.

The injection system of these engines and these control means have,however, never before been used to control the stopping and restartingof an engine in a determined position.

In the case of engines with indirect injection (i.e. with injection intothe inlet manifolds of the cylinders) and with spark ignition, thestarting time is relatively long (generally greater than 0.5 seconds).The engine computer of modern vehicles has to go through a succession ofhighly precise stages before it reaches a normal operation configurationto control the engine after it has started. The time devoted to thisprocess significantly increases the starting times, which are generallymuch longer than starts carried out with a conventional systemcomprising a carburetor and a contact breaker.

With each starting, the computers of modern vehicles have to synchronizethe injection and the ignition, then give the order to inject and,finally, control the ignition.

Furthermore, this process causes pollution, as the first injections intothe manifold are not synchronized; the injections are carried out onall, or almost all, of the cylinders; petroleum feedstock is releasedand can thus generally damage the catalyst, placed on the exhaust line,and/or cause pollution.

It seems necessary to reduce the starting times and limit the pollutingemissions of modern engines, in particular for implementing a so-called“stop and start” operation, which is implemented automatically by thecomputer of a motor vehicle to stop and restart the vehicle, as afunction of the traffic conditions. In particular, when the vehiclestops, for example because it is in a queue of vehicles which havestopped, the computer controls the stopping of the engine and then itsrestarting when the vehicle can move off again.

In this case, as the engine generally stops only for a short period,starting is carried out while the engine is hot, and it is necessary toobtain very rapid hot restart conditions for the spark ignition engine,which do not produce additional pollution in the exhaust gases.

The object of the invention is therefore to propose a method of stoppingand restarting an internal combustion engine with indirect injection andspark ignition, comprising at least one cylinder, in which a piston, afuel inlet manifold communicating with the cylinder, and a rotating partset in rotation by the piston, via a connecting rod, which allows veryrapid hot restarts to be carried out and does not produce any additionalpollution in the exhaust gases, move.

With this object:

-   -   the speed of rotation and the position of the piston and of the        rotating part of the engine are measured continuously, and the        fuel injection is cut off at predetermined speed and angular        position values of the rotating part of the engine, in order to        stop the piston and the rotating part in a predetermined        position    -   a fuel feedstock is injected into the inlet manifold of the        cylinder, in the intake phase, during the last revolution of the        engine before it stops in a predetermined position,    -   in order to restart the engine after it has been stopped by        setting the rotating part of the engine in rotation, the        implementation of the compression phase in the cylinder is        identified and ignition of the feedstock is carried out in the        cylinder in the compression phase, and    -   the successive feedstock injection and ignition in at least one        cylinder are carried out according to a predetermined sequence,        in order to optimize consumption and emissions and to limit        overspeeding of the engine during starting, thus improving the        quality of the start.

To carry out the restarting, according to the invention, a desiredquantity of fuel, which is determined during the development of therapid hot starting operations, is injected into the cylinder.

In order to facilitate understanding of the invention, a method ofstopping and restarting an internal combustion engine with sparkignition and indirect injection, according to the invention, will bedescribed by way of example.

FIG. 1 is a diagram showing the means used to implement the method ofstopping and restarting an engine with direct injection and sparkignition, according to the invention.

FIG. 2 is a comparative diagram showing the stopping phases of an enginein the case of a stop according to the prior art and, of an engine, thestopping of which is controlled according to the method of theinvention.

FIG. 3 is a comparative diagram showing the hot reheating phases of anengine controlled according to the prior art and of an engine controlledaccording to the method of the invention.

FIG. 4 is a schematic view showing the means for measuring the angularposition of a crankshaft of a spark ignition engine, used during a rapidrestarting of the engine, according to the method of the invention.

FIG. 5 is a logic diagram showing the course of a method of restarting aspark ignition engine, according to the invention.

FIG. 6 is a comparative diagram showing the curves of an increase inspeed during the starting of an engine by the method of the inventionand by a method according to the prior art.

FIG. 1 shows schematically a thermal engine 1, which is, for example, anin-line four-cylinder engine.

The engine 1 comprises four cylinders (referred to hereinafter as C₁,C₂, C₃, C₄), in each of which a piston, which is connected, via aconnecting rod, to a crankshaft 2 that is integral, at one of its ends,with a flywheel 3, moves.

The pistons with alternating movements, the connecting rods and thecrankshaft 2 and flywheel 3, which can be set in rotation, represent allof the mobile elements of the engine 1.

The engine 1 comprises a starter 4, which may consist of an electricmotor or of a reversible alternator. The starter 4 comprises a controlelement 4′, which allows the electrical supply of the starter 4 from thebattery of the motor vehicle to be established or cut off.

The engine 1 is an engine with indirect injection of fuel into the inletmanifolds of each of the cylinders of the engine. The injectors arecontrolled by an electronic control box 5, which allows the injectionsto be synchronized with the displacement of the mobile elements of theengine 1.

The motor vehicle in which the engine 1 is installed comprises acomputer 6, which allows various functions for monitoring andcontrolling the motor vehicle, and in particular the engine 1, to beperformed.

In particular, the computer 6 is connected to the box 5 controlling theinjection of fuel into the cylinders of the engine, so as to synchronizethe fuel injection with the position of the pistons and to stop theinjection of fuel into the inlet manifolds of the cylinders at adetermined moment, so as to stop the engine in a desired position.

A sensor 7 (or a plurality of sensors) is/are arranged near the flywheel3, in order to measure the instantaneous speed of rotation of the engineand to determine, at any given moment, the angular position of theflywheel 3 and the crankshaft 2, corresponding to a defined position ofeach of the pistons inside the in-line cylinders of the engine 1.

The information from the sensor 7 is transmitted to the computer 6,which is programmed to determine, when there is a command to stop theengine, the precise moment at which the order to cut off the injectionshould be transmitted to the box 5.

In the event of the computer 6 commanding a “stop and start” operation,i.e. a stop and automatic restart of the engine 1 of the motor vehicle,as a function of the traffic conditions, the computer 6 is connected tothe control box 4′ of the starter 4.

In the case of a spark ignition engine, the ignition control box is alsoconnected to the computer 6. In this case, it is assumed in FIG. 1 thatthe box 5 controls both the injection of fuel into the cylinders and theignition of the fuel injected into the cylinders.

During implementation of the “stop and start” operation, the computer 6receives information which allows it to determine whether an order tostop the engine 1 of the motor vehicle should be given. When theconditions for stopping the engine are combined, the computer 6determines, from the speed and the angular position of the rotating part2, 3 of the engine, which are transmitted by sensors, such as the sensor7, the exact moment at which an order to interrupt the fuel injectionand/or to interrupt the ignition should be transmitted to the controlbox 5.

The program of the computer allows the exact moment to be determined atwhich the order to interrupt the injection should be transmitted, inorder to stop the engine in a well-determined position, which isselected to facilitate the subsequent restarting of the engine.

The stopping position is stored in the computer, to be taken intoaccount in a later restarting of the engine.

In the case of a spark ignition engine, the interruption of the ignitionand the interruption of the fuel injection can be controlledsimultaneously.

The fuel injection and the ignition can also be interrupted at separatemoments. The production of unburned fuel in the cylinders and exhaustline can thus be avoided, which allows exhaust gas pollution to bereduced and deterioration of the catalyst container to be limited.

Generally, the interruption of the injection of fuel into the cylindersof the engine at an optimally determined moment, as a function of thespeed and the angular position of the crankshaft, prevents, inparticular, the stopping of the engine from being activated in themiddle of an injection phase in a cylinder. Exhaust gas pollution isthus reduced and the service life of the catalytic container, in thecase of a petrol engine, and of the particulate filter (PF), in the caseof a diesel engine, is lengthened. The efficiency of the “stop andstart” system is thus improved significantly, and the possibilities ofincorporating it into the engine control of the motor vehicle areincreased.

From the precise stopping position of the engine, which is stored, it iseasy to determine in which cylinder the fuel must be injected first, atthe moment of restarting.

It is therefore no longer necessary, as was the case in the prior art,to supply all the cylinders simultaneously, which causes exhaust gaspollution and reduces the service life of the catalytic container (or ofthe particle filter).

The quantity of fuel injected and the ignition angle of the firstcombustions are specific to the rapid hot start. This open-loopoperation is determined by specific development of the hot restart. Therichness control is activated as quickly as possible, in order toprevent pollution. The ignition angle allows, in particular, enginerevving to be used in order to improve the quality and the smoothness ofthe start.

Moreover, restarting is carried out very quickly and with significantlyincreased regularity, as will be illustrated in greater detail withreference to FIG. 3 and FIG. 6.

Finally, the fact that the position of the crankshaft during starting isoptimally determined and known allows an electric starting machinehaving ideal characteristics to be selected.

FIG. 2 shows in diagrammatic form the speed of rotation of the engine asa function of the angular position of the crankshaft and the stoppingphases of the engine, in the case of the prior art (upper curve 8) andin the case of the invention (lower curve 10).

In the case of the prior art, stopping can be carried out in two ranges9 and 9′, the angular position of the crankshaft extending either sideof a central position, over 30°. There are thus two stoppingpossibilities, with an inaccuracy of 30° either side of the theoreticalstopping position, i.e. four different positions according to thephases, over an engine cycle.

In the case of the invention (lower curve 10), stopping can be carriedout in a single range 11 of the angular position of the crankshaft.

As can be seen from FIG. 3, during restarting of the engine after a stopcontrolled according to the prior art (upper part of the figure), theengine, according to the actual stopping position of the mobile elementsof the engine, can be stopped after a number of rotations of the movingrotating part of the engine ranging from two to six.

In the case of a stop programmed and determined according to theinvention, restarting with an injection of fuel into a well-determinedcylinder allows starting, i.e., a first combustion in the cylinders ofthe engine, to be achieved in approximately a quarter of a revolution ofthe crankshaft. If there is no injection during the last revolutionbefore stopping, starting is carried out in one and a quarterrevolutions.

The method according to the invention thus allows the use of the starterto be greatly reduced, and restarting to be accelerated, with lessexhaust gas pollution.

In the case of a spark ignition engine for rapid hot restarting of theengine, for example in operation of the “stop and start” type, themethod of controlling the stopping of the engine according to theinvention is used, so as to obtain a programmed stopping position of themobile elements of the engine, this position being stored by thecomputer of the motor vehicle.

The stopping of the engine is controlled by the interruption of the fuelinjection and/or by the interruption of the ignition, it being possibleto give the two corresponding cut-off orders simultaneously or atdifferent moments.

Furthermore, when the engine is stopped, during the last revolutionbefore it stops, fuel feedstock is injected into the inlet manifold of acylinder of the engine, in the intake phase, in order to prepare therestarting of the engine. This injection is carried out in a precisemanner, in a first well-determined position of the rotating part of theengine, and therefore of the piston or pistons in the cylinder orcylinders. At least two injections into inlet manifolds ofwell-determined cylinders of the engine can also be carried out duringstopping.

Furthermore, in order to restart after stopping in a determined positionof the mobile elements of the engine, with injection of feedstock intothe cylinders of the engine during stopping, ignition of the feedstockis carried out from the first revolution of the crankshaft, bycontrolling, using a, physical target that is integral with thecrankshaft, the precise position of the moving parts of the engine. Theignition of the fuel feedstock is thus controlled in the cylinderstopped in the compression position, then in the cylinder stopped in theintake phase. These ignitions correspond to second well-determinedpositions of the rotating part of the engine. More generally, acalibrated injection and an ignition of the fuel feedstock are carriedout in sequence in the cylinders of the engine, in a predeterminedorder.

It should be noted that, unlike the case of engines with directinjection of fuel into the cylinders, the injection of feedstock duringthe stopping of the engine has to be carried out, in the case of engineswith indirect injection, into manifolds of cylinders that arewell-determined and generally in the intake phase. Injection must alsobe carried out just before the engine stops, in the last revolutionbefore it stops. The injection of metered feedstock into awell-determined cylinder allows fuel consumption and pollutant emissionsin exhaust gases to be reduced.

As can be seen from FIG. 4, the flywheel 3, which is integral with thecrankshaft 2, carries two targets 12 and 12′, placed at 180° from eachother, with regard to a revolution about the common axis of the flywheel3 and the crankshaft 2.

The sensor 7, which is preferably a Hall effect sensor, detects themovement of the targets 12 and 12′ into a position corresponding to thetop dead center of the pistons in the cylinders of the engine.

During movement of a target, the sensor 7 controls, over a very shorttime, the charging of one of the coils carrying out the ignition in acylinder, and causes ignition in the cylinder. Ignition is thus causedin a cylinder in compression very shortly after the engine has been setin rotation for the restart, as a precise stopping position of theengine is obtained and the first cylinder in compression, in whichignition has to be carried out, is determined. Ignition in the firstcylinder in compression is carried out after no more than a quarter of arevolution of the crankshaft.

The injection of fuel during the stoppage of the engine can be carriedout in such a way as to limit consumption and exhaust gas pollution.Indeed, it is not essential to inject fuel into all the cylinders afterthe order to stop the engine, but only those which will serve to rapidlyrestart the engine, i.e., substantially, the cylinder of which thepiston stops in the compression phase and optionally that of which thepiston stops in the intake phase. The expedient moment for injectingfuel into the desired cylinders can be deduced from the measurementcarried out by an appropriate sensor, which may be the sensor 7 shown inFIGS. 1 and 4, of the engine speed during the stop.

In order to control the ignition at the moment of restarting the engine,it is also possible to arrange four targets on the camshaft of theengine and a Hall effect sensor in a position allowing the movement ofthe targets to be detected.

The Hall effect sensor of the movement of the targets of the camshaft ispreferably used to determine the phases in the cylinders of the engine,the Hall effect sensor, which is associated with the flywheel that isintegral with the crankshaft, preferably being used to control ignitionin the cylinders carrying out the start.

The oval shapes on the left-hand side of the logic diagram in FIG. 5show the various phases of operation of the engine, the rectangles inthe central part of the logic diagram show the actions performed on thecomponents of the engine, and the diamonds in the right-hand part of thelogic diagram show the actions performed by the computer to stop andstart the engine.

The logic diagram in FIG. 5 was designed for a stop and restart, tocarry out a “stop and start” operation.

An induction sensor, placed near the flywheel that is integral with thecrankshaft, is used to control the ignition and the injections of fuelinto the desired cylinders, and a Hall effect sensor of the movement offour targets, which are integral with the camshaft, is used to recognizethe phases of the engine.

The various states of the engine, which correspond to the oval shapes inthe left-hand part of the logic diagram, are identified by the referencenumerals 13 to 18, which correspond to the following actions:

-   13: the engine rotates at idling speed,-   14: the engine decelerates from its idling speed,-   15: the engine has stopped,-   16: the engine starts its first revolution,-   17: acceleration of the engine,-   18: the engine has started.

The corresponding functions performed on the engine components areindicated in the rectangular shapes 19 to 24, the meanings of which aregiven below:

-   19: cutting-off of the ignition and the injection of the engine,-   20: prediction of the stopping phase of the engine and injection of    fuel during the last revolution of the engine,-   21: control of the starter,-   22: ignition in the cylinder C₁, stopped in the compression phase,-   23: ignition in the cylinder C₃, stopped in the intake phase,-   24: transition of the computer to standard operation for ignition of    the engine.

The actions performed by the computer, shown in the diamond shapes 25 to30, are as follows:

-   25: decision of the computer to stop the engine, in order to carry    out the “stop and start” operation,-   26: calculation of the variations in engine speed from the    measurements of the sensor associated with the flywheel, then from    the sensor associated with the camshaft, in the last revolutions of    the engine,-   27: decision of the computer to restart the engine, in order to    carry out the “stop and start” operation,-   28: start of the charging of a coil upon movement of a target in    front of the sensor associated with the camshaft, and injection of    fuel into the manifold of the cylinder C₄, in the exhaust phase,-   29: transition to the calculation of advance and of conventional    injection into the engine,-   30: checking of the synchronization of the computer with the sensor    associated with the crankshaft.

The logic diagram in FIG. 5 and tables 1, 2 and 3 below explain theimplementation of the method according to the invention in order to stopand restart a spark ignition engine, in optimal conditions for carryingout the “stop and start” operation.

The sequence of processes in the cylinders will be described in tables1, 2 and 3, with the following abbreviated references:

-   Int Intake-   Inj Injection-   Exh Exhaust-   Comp Compression-   Comb Combustion-   Rel Release-   I Ignition-   CSt Complete stop of engine

Table 1 gives the process sequences in each of the cylinders, duringnormal operation of the engine.

TABLE 1 1 cycle = 2 revolutions of crankshaft (720°) = 4 Cylindersphases C₁ Exh Int/Inj Comp I Comb/Rel Exh Int/Inj C₂ Int/Inj Comp IComb/Rel Exh Int/Inj Comp C₃ I Comb/Rel Exh Int/Inj Comp I Comb/Rel ExhC₄ Comp I Comb/Rel Exh Int/Inj Comp I Comb/Rel

The ignition order of the cylinders is as follows: C₁, C₃, C₄, C₂, C₁,etc.

As the motor vehicle has stopped and the engine is rotating at idlingspeed, the computer decides to stop the engine in order to carry out the“stop and start” operation. The computer controls the cutting-off of theignition and the injection (optionally at different moments) The enginedecelerates from idling speed and, as the engine stops, the computerdetermines the variation in the speed of the engine and the stoppingposition.

During the last revolution of the engine, a single injection of fuel iscarried out into at least one of the cylinders, and two fuel feedstocksare generally injected into the cylinder whose piston stops incompression and into the cylinder in which the piston stops in theintake phase. Table 2 gives the process sequences in each of thecylinders C₁, C₂, C₃, and C₄, during the stopping phase of the engine.

TABLE 2 Cylinders Last revolution CSt C₁ Rel Exh Int/Inj Comp C₂ Exh IntComp Rel C₃ Comp Rel Exh Int/Inj C₄ Int Comp Rel Exh

Stopping of the Engine

During the stopping phase of the engine, the injection and the ignitionare cut off. There is no combustion.

During the last revolution, fuel is injected into the cylinders in whichignition will be carried out first after restarting, i.e. into thecylinder C₁, in which a complete intake phase is carried out during thelast revolution of the engine, and which is in the compression phase, atthe moment of complete stopping, and in the cylinder C₃, in the intakephase, at the moment of stopping.

After the engine has stopped, the computer decides to restart theengine, in order to complete the “stop and start” operation. Thecomputer controls the supply of the starter and the engine starts itsfirst revolution.

During the movement of a target in front of the sensor of the camshaft(Hall effect sensor), the computer controls the start of the charging ofan ignition coil corresponding to the cylinder C₁, stopped incompression. At the same time, the computer controls an injection offuel into the manifold of the cylinder C₄, stopped in the exhaust phase.Ignition is then carried out in the cylinder C₁, stopped in compression,either after a minimal time of charging the coil (timed ignition), orwhen the high-to-low transition of the signal of the target isidentified.

The engine is then accelerated by the displacement of the piston, whichhad stopped in compression in the cylinder C₁.

The computer then proceeds to a conventional method of calculatingignition and injection for control of the engine, this transition beingmade either at the start of the charging of the coil, by means of themovement of a target in front of the sensor of the camshaft, or byidentifying missing teeth on the toothing of the flywheel.

Ignition is then carried out in the cylinder C₃, in which the piston hadstopped in intake at the moment the engine stopped. The engine is thenstarted and controlled by the computer in the standard operation. Therestarting phase is described in table 3 below.

The processes carried out in the cylinders C₁, C₂, C₃ and C₄ duringrestarting are described in table 3.

TABLE 3 Cylinders CSt First revolution C₁ Comp I Comb/Rel Exh Int/Inj C₂Rel Exh Int/Inj Comp C₃ Int/Inj Comp I Comb/Rel Exh C₄ Exh Int/Inj CompI Comb/Rel

Stopping of the Engine

Ignition is controlled in the cylinder C₁, where the air-petrol mixturewas prepared before stopping, then compressed, then in the cylinder C₃.The other cylinders follow their normal sequence.

The main advantages of the method according to the invention are that itprovides a high degree of regularity in the stopping of the engine, witha low dispersion of the stopping position. This is beneficial forrestarting the engine, improves synchronization of the injection withthe phases of the cylinders of the engine, and reduces exhaust gaspollution.

In the case of a spark ignition engine, the method according to theinvention allows starting to be carried out from the first revolution ofthe crankshaft. This is highly beneficial in the implementation of the“stop and start” operation.

FIG. 6 shows the variations in the speed of an engine with indirectinjection and spark ignition, as a function of time, during a hotrestart, in the case of a stop and restart carried out according to theinvention (curve 31) or according to a common technique of implementingthe “stop and start” operation (curve 32).

In the case of the method according to the invention, a stable speed isreached more quickly and at a substantially lower level of engine speed.

Rotational overspeeding of the engine at the moment of starting(overshoot), as well as fuel consumption and pollutant emissions fromthe exhaust, are thus limited significantly.

Starting is also smoother, which is of great importance as far ascomfort in the engine-powered motor vehicle and long-term maintenance ofthe engine are concerned.

In particular, precise calibration of the sequential injections carriedout into cylinders and of the ignition at the moment of restartingallows a smooth restart to be obtained by limiting oscillations, bycontrolling the injected quantities and the opening times of the intakevalves.

Precise control of the injections and the ignition during startingallows oscillations to be reduced.

The invention is not strictly limited to the embodiments that have beendescribed.

The angular position of the crankshaft or the camshaft of the engine canthus be identified in a different manner from those which have beendescribed, by using any type of target and appropriate sensor.

The measurements of speed and of the position of the crankshaft can becarried out by any means present in the motor vehicle, or by anyspecific means used to carry out the method of the invention.

In the case of a spark ignition engine, the injections during the phaseleading to the stopping of the engine must be carried out in a veryprecise manner, which can necessitate the use of particular means.

The invention applies to any engine with indirect injection and sparkignition.

In the case of a spark ignition engine, the engine can be stopped byinterrupting the ignition and/or the injection, it being possible tocarry out these two processes simultaneously or separately. Uponrestarting, the ignition control at a precise moment in the cylinder incompression, at the moment when the engine stops, then in the cylinderin the intake position during stopping, allows the engine to be startedfrom the first revolution of the crankshaft, in a reproducible manner.

The invention applies, in particular, to motor vehicles of which thecomputer allows the “stop and start” operation to be performed in orderto stop and restart the engine, in an automatic manner.

1. Method of stopping and restarting an internal combustion engine withindirect injection and spark ignition, comprising at least one cylinder,in which a piston, a fuel inlet manifold communicating with the cylinderand a rotating part set in rotation by the piston, via a connecting rod,move, wherein: the speed of rotation and the position of the piston andof the rotating part of the engine are measured continuously, and thefuel injection is cut off at predetermined speed and angular positionvalues of the rotating part of the engine in order to stop the pistonand the rotating part in a predetermined position, a fuel feedstock isinjected into the inlet manifold of one of the cylinders which is in theintake phase, during the last revolution of the engine before it stopsin a predetermined position, upon restarting the engine, after it hasstopped, by setting the rotating part of the engine in rotation, theimplementation of the compression phase in the cylinder is identifiedand ignition of the feedstock is carried out in the cylinder in thecompression phase, and the successive feedstock injection and ignitionin at least one cylinder are carried out according to a predeterminedsequence, in order to optimize consumption and emissions and to limitoverspeeding of the engine during starting, thus improving the qualityof the start.
 2. Method according to claim 1, wherein the speed and theangular position of the rotating part of the engine are measured usingat least one sensor, which senses the speed and the angular position ofa flywheel that is integral with a crankshaft of the engine.
 3. Methodaccording to claim 1, wherein: the speed of rotation and the angularposition of the rotating part of the engine are measured continuously,and in order to stop the mobile parts of the engine in a predeterminedposition that facilitates restarting of the engine, the ignition and/orfuel injection is/are interrupted at predetermined speed and angularposition values of the rotating part of the engine.
 4. Method accordingto claim 3, wherein the speed and angular position of the rotating partof the engine are determined using a sensor, which senses the speed andthe angular position of a flywheel that is integral with a crankshaft ofthe engine and/or a camshaft for controlling the valves of the engine.5. Method according to claim 1, wherein the engine is restarted in nomore than a quarter revolution of the assembly of the engine, and in oneand a quarter revolutions if injection is not carried out during thelast revolution before stopping.
 6. Method according to claim 1, in thecase of an engine comprising a plurality of cylinders, and preferablyfour cylinders, in line, wherein, during the last revolution before theengine stops, preceding the restart, fuel feedstocks are injected intothe inlet manifold of the cylinder of the engine, in which the piston isin the intake position during the last revolution before the enginestops and in the compression position at the moment of stopping, andinto a second cylinder of the engine, in the intake phase, at the momentof stopping.
 7. Method according to claim 1, wherein, in order torestart the engine, ignition is carried out in the cylinder, the pistonof which is in the compression position at the moment when the enginestops, then in the cylinder, in which the piston is in the intakeposition at the moment when the engine stops.
 8. Method according toclaim 1, wherein the sequential injections and the ignition to becarried out during the restart are precisely calibrated, and thesequential injections and the ignition are carried out according to thevalues obtained from the calibration.
 9. Method according to claim 8,wherein the quantities of fuel to be injected sequentially into thecylinders and the ignition angles, during restarting of the engine, aredetermined from the calibration.
 10. Method according to claim 2,wherein: the speed of rotation and the angular position of the rotatingpart of the engine are measured continuously, and in order to stop themobile parts of the engine in a predetermined position that facilitatesrestarting of the engine, the ignition and/or fuel injection is/areinterrupted at predetermined speed and angular position values of therotating part of the engine.
 11. Method according to claim 10, whereinthe speed and angular position of the rotating part of the engine aredetermined using a sensor, which senses the speed and the angularposition of a flywheel that is integral with a crankshaft of the engineand/or a camshaft for controlling the valves of the engine.
 12. Methodaccording to claim 2, in the case of an engine comprising a plurality ofcylinders, and preferably four cylinders, in line, wherein, during thelast revolution before the engine stops, preceding the restart, fuelfeedstocks are injected into the inlet manifold of the cylinder of theengine, in which the piston is in the intake position during the lastrevolution before the engine stops and in the compression position atthe moment of stopping, and into a second cylinder of the engine, in theintake phase, at the moment of stopping.
 13. Method according to claim3, in the case of an engine comprising a plurality of cylinders, andpreferably four cylinders, in line, wherein, during the last revolutionbefore the engine stops, preceding the restart, fuel feedstocks areinjected into the inlet manifold of the cylinder of the engine, in whichthe piston is in the intake position during the last revolution beforethe engine stops and in the compression position at the moment ofstopping, and into a second cylinder of the engine, in the intake phase,at the moment of stopping.
 14. Method according to claim 4, in the caseof an engine comprising a plurality of cylinders, and preferably fourcylinders, in line, wherein, during the last revolution before theengine stops, preceding the restart, fuel feedstocks are injected intothe inlet manifold of the cylinder of the engine, in which the piston isin the intake position during the last revolution before the enginestops and in the compression position at the moment of stopping, andinto a second cylinder of the engine, in the intake phase, at the momentof stopping.
 15. Method according to claim 5, in the case of an enginecomprising a plurality of cylinders, and preferably four cylinders, inline, wherein, during the last revolution before the engine stops,preceding the restart, fuel feedstocks are injected into the inletmanifold of the cylinder of the engine, in which the piston is in theintake position during the last revolution before the engine stops andin the compression position at the moment of stopping, and into a secondcylinder of the engine, in the intake phase, at the moment of stopping.16. Method according to claim 2, wherein, in order to restart theengine, ignition is carried out in the cylinder, the piston of which isin the compression position at the moment when the engine stops, then inthe cylinder, in which the piston is in the intake position at themoment when the engine stops.
 17. Method according to claim 3, wherein,in order to restart the engine, ignition is carried out in the cylinder,the piston of which is in the compression position at the moment whenthe engine stops, then in the cylinder, in which the piston is in theintake position at the moment when the engine stops.
 18. Methodaccording to claim 4, wherein, in order to restart the engine, ignitionis carried out in the cylinder, the piston of which is in thecompression position at the moment when the engine stops, then in thecylinder, in which the piston is in the intake position at the momentwhen the engine stops.
 19. Method according to claim 3, wherein thesequential injections and the ignition to be carried out during therestart are precisely calibrated, and the sequential injections and theignition are carried out according to the values obtained from thecalibration.
 20. Method according to claim 5, wherein the sequentialinjections and the ignition to be carried out during the restart areprecisely calibrated, and the sequential injections and the ignition arecarried out according to the values obtained from the calibration.